Mass termination, insulation displacement connectors have come into increasing commercial prominence because of the significant savings in time and labor they offer compared to stripping and individually terminating each conductor using a crimp terminal. These connectors have an insulative housing body holding a number of regularly spaced terminal elements having slotted plates terminating in sharpened free ends extending beyond a surface of the body. The conductors also include covers having recesses in a facing surface for receiving the free ends of the plates. After the insulated conductors are aligned with their corresponding slotted plates, relative closing of the housing body and cover results in displacement of the insulation with the conductor cores contacting the metallic plates. For further information regarding the operation and structure of such mass termination connectors, reference may be made to U.S. Pat. Nos. 4,458,967 and 3,912,354.
The most efficient form of conductors for use with such connectors is the flat cable in which conductors, running parallel and spaced to match the spacing of the terminal elements in the connector, are held by a layer of insulation. The use of a flat cable avoids running the conductors one at a time and holding them in position for termination. The flat cable can be used for either a daisy chain connection (where the connector is applied intermediate the cable ends) or an end connection. The sharpened ends of the slotted plates pierce the web material between the conductors in the flat cable as the body and cover close so slitting of the cable between conductors is not required.
While flat cables offer many advantages with respect to efficiency in termination, they present difficulties during routing. Flat cables have certain dimensions larger than comparable round cables, the flat cables do not bend as easily, they are more susceptible to damage during routing, and the continuous presence of the layer of insulation holding the discrete conductors may result in somewhat increased weight of a flat cable.
There are several methods for manufacturing flat cable. In one method, the insulation is extruded about parallel, coplanar conductors. In another, two layers of insulation are bonded together with the conductors held in parallel, coplanar relationship. Some of these methods require the use of large expensive manufacturing equipment. One simpler manufacturing method has been proposed wherein individual conductors, each having a thermoplastic jacket, are positioned on a layer of the same material as that used in the jackets. Upon raising the temperature to the melting point of the insulation, the jackets and layer will fuse, forming a flat cable. Unfortunately, the most commonly used insulating materials, such as polyvinyl chloride, have poor dimensioned stability, particularly when the flat cable is subjected to varying temperatures.
A method of forming flat cable using conductor modules has also been suggested. In this method, pairs of conductors are formed into modules by applying a jacket of insulation about them. The modules are fed in edge-to-edge relationship between two webs of polyester material precoated with a hot-melt adhesive on their facing surfaces. This assembly is then subjected to heating and the application of pressure to form the final flat cable assembly. For additional information concerning this flat cable and its method of manufacture, reference may be made to U.S. Pat. No. 4,468,089.
Another flat cable includes twisted pairs of wires having straight wire portions wherein the wires are maintained in their spaced, parallel relationships by means of discrete insulative strips. Yet another flat cable includes twisted pair sections spaced by straight wire portions with upper and lower films extending the entire length of the cable with the films heat welded between conductors. For further information regarding the structure and operation of these cables, reference may be made to U.S. Pat. Nos. 3,459,878 and 4,096,006, respectively.